mem.c

#define _GNU_SOURCE
#include <ctype.h>
#include <inttypes.h>
#include <setjmp.h>
#include <signal.h>
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>
#include <sysexits.h>
#include <unistd.h>

static sigjmp_buf env;

static void skip(int signo) {
    siglongjmp(env, signo);
}

int main(int argc, const char *const *argv) {
    const struct sigaction sa_skip = { .sa_handler = skip };
    struct sigaction old_sigbus, old_sigsegv;
    FILE *fp;
    uintptr_t addr0, addr1;
    char readable;

    fp = fopen("/proc/self/maps", "r");
    if (!fp) {
        perror("Failed to open /proc/self/maps");
        exit(EX_OSFILE);
    }
    sigaction(SIGBUS, &sa_skip, &old_sigbus);
    sigaction(SIGSEGV, &sa_skip, &old_sigsegv);
    while (fscanf(fp, "%"SCNxPTR"-%"SCNxPTR" %c%*[^\n]\n", &addr0, &addr1, &readable) > 2) {
        for (ptrdiff_t off0 = 0, off1; off0 < addr1 - addr0; off0 += 16) {
            printf("%08"PRIxPTR":", addr0 + off0);
            for (off1 = off0; off1 < addr1 - addr0 && off1 < off0 + 16; off1++) {
                if (~(off0 ^ off1) & 1) {
                    printf(" ");
                }
                if (!sigsetjmp(env, 1) && readable == 'r') {
                    printf("%02x", *(unsigned char *) (addr0 + off1));
                } else {
                    printf("??");
                }
            }
            printf("%*s", (int) (off0 + 16 - off1) * 5 / 2 + 2, "");
            for (off1 = off0; off1 < addr1 - addr0 && off1 < off0 + 16; off1++) {
                char c = !sigsetjmp(env, 1) && readable == 'r' ? *(char *) (addr0 + off1) : 0;
                printf("%c", isprint(c) ? c : '.');
            }
            printf("\n");
        }
    }
    sigaction(SIGSEGV, &old_sigsegv, NULL);
    sigaction(SIGBUS, &old_sigbus, NULL);
    fclose(fp);
}